Both kings and emperors are monarchs, but emperor and empress are considered the higher monarchical titles. Inasmuch as there is a strict definition of emperor, it is that an emperor has no relations implying the superiority of any other ruler, and typically rules over more than one nation. Thus a king might be obliged to pay tribute to another ruler[citation needed], or be restrained in his actions in some unequal fashion, but an emperor should in theory be completely free of such restraints. However monarchs heading empires have not always used the title—the British sovereign did not assume the title until the incorporation of India into the British Empire, and used it to symbolise British control over all its territories, even those lying outside actual British India, the reason being that India was the jewel in the crown of the British Empire. Similarly before the 19th century the term Emperor in Europe referred exclusively to the Holy Roman Emperor, despite the fact that the empire neither contained Rome nor did it exercise much power beyond the German speaking states, by the late 16th century the empire itself came to mean the dynastic lands held by the Habsburgs and following the Thirty Years' War the Habsburg emperors control over the German states outside Habsburg Austria became nearly non-existent, the position of Emperor however continued till the early 19th century, before it was abolished by Francis II who became the first Emperor of Austria. For purposes of protocol, emperors were once given precedence over kings in international diplomatic relations; currently, however, precedence amongst heads of state – whether they be Kings, Queens, Emperors, or Presidents – is determined by the duration of time that each one has been continuously in office.

Outside the European context, emperor was the translation given to holders of titles who were accorded the same precedence as European emperors in diplomatic terms. In reciprocity, these rulers might accredit equal titles in their native languages to their European peers. Through centuries of international convention, this has become the dominant rule to identifying an emperor in the modern era.

Some empires, such as the Holy Roman Empire and the Russian Empire, derived their office from the authority of the Roman Emperors (translatio imperii). The title was a conscious attempt by monarchs to link themselves to the institutions and traditions of the Romans as part of state ideology. Historians have liberally used emperor and empire anachronistically and out of its Roman and European context to describe any large state from the past or the present. Such pre-Roman titles as "Great King" or "King of Kings", used by the Kings of Persia and others, are often considered as the equivalent. Sometimes this reference has even extended to non-monarchically ruled states and their spheres of influence such as the "Athenian Empire" of the late 5th century BC, the "Angevin Empire" of the Plantagenets, the Soviet, and American "empires" of the Cold War era. However such "empires" did not need to be headed by an "emperor". Empire became identified instead with vast territorial holdings rather than the title of its ruler by the mid-18th century.

The title was first used as an honorific for a military leader in ancient Rome, meaning commander or general.

In the Roman tradition a large variety in the meaning and importance of the imperial form of monarchy developed: in intention it was always the highest office, but it could as well fall down to a redundant title for nobility that had never been near to the "Empire" they were supposed to be reigning. Also the name of the position split in several branches of Western tradition, see below.

The importance and meaning of coronation ceremonies and regalia also varied within the tradition: for instance Holy Roman Emperors could only be crowned emperor by the Pope, which meant the coronation ceremony usually took place in Rome, often several years after these emperors had ascended to the throne (as "king") in their home country. The first Latin Emperors of Constantinople on the other hand had to be present in the newly conquered capital of their empire, because that was the only place where they could be granted to become emperor.

Early Roman Emperors avoided any type of ceremony or regalia different from what was already usual for republican offices in the Roman Republic: the most intrusive change had been changing the color of their robe to purple. Later new symbols of worldly and/or spiritual power, like the orb, became an essential part of the imperial accessories.

Rules for indicating successors also varied: there was a tendency towards maleinheritance of the supreme office, but as well election by noblemen, as ruling empresses (for empires not too strictly under salic law) are known. Ruling monarchs could additionally steer the succession by adoption, as often occurred in the two first centuries of Imperial Rome. Of course, intrigue, murder and military force could also mingle in for appointing successors; the Roman imperial tradition made no exception to other monarchical traditions in this respect. Probably the epoch best known for this part of the imperial tradition is Rome's third century rule.

When Republican Rome turned into a de factomonarchy in the second half of the 1st century BC, at first there was no name for the title of the new type of monarch. Ancient Romans abhorred the name Rex ("king")[citation needed], and it was critical to the political order to maintain the forms and pretenses of republican rule. Julius Caesar had been Dictator, an acknowledged and traditional office in Republican Rome. Caesar was not the first to hold it, but following his assassination the term was abhorred in Rome[citation needed].

Augustus, considered the first Roman emperor, established his by collecting on himself offices, titles, and honours of Republican Rome that had traditionally been distributed to different people, concentrating what had been distributed power in one man. One of these offices was princeps senatus, ("first man of the Senate") and became changed into Augustus' chief honorific, princeps civitatis ("first citizen") from which the modern English word and title prince is descended. The first period of the Roman Empire, from 27 BC – 284 AD, is called the principate for this reason. However, it was the informal descriptive of Imperator ("commander") that became the title increasingly favored by his successors. Previously bestowed on high officials and military commanders who had imperium, Augustus reserved it exclusively to himself as the ultimate holder of all imperium. (Imperium is Latin for the authority to command, one of a various types of authority delineated in Roman political thought.)

Beginning with Augustus, Imperator appeared in the title of all Roman monarchs through the extinction of the Empire in 1453. After the reign of Augustus' immediate successor Tiberius, being proclaimed imperator was transformed into the act of accession to the head of state. Other honorifics used by the Roman Emperors have also come to be synonyms for Emperor:

Caesar (as, for example, in Suetonius' Twelve Caesars). This tradition continued in many languages: in German it became "Kaiser"; in certain Slavic languages it became "Tsar"; in Hungarian it became "Császár", and several more variants. The name derived from Julius Caesar's cognomen "Caesar": this cognomen was adopted by all Roman emperors, exclusively by the ruling monarch after the Julio-Claudian dynasty had died out. In this tradition Julius Caesar is sometimes described as the first Caesar/emperor (following Suetonius). This is one of the most enduring titles, Caesar and its transliterations appeared in every year from the time of Caesar Augustus to Tsar Symeon II of Bulgaria's removal from the throne in 1946.

Augustus was the honorific first bestowed on Emperor Augustus: after him all Roman emperors added it to their name. Although it had a high symbolical value, something like "elevated" or "sublime", it was generally not used to indicate the office of Emperor itself. Exceptions include the title of the Augustan History, a semi-historical collection of Emperors' biographies of the 2nd and 3rd century. Augustus had (by his last will) granted the feminine form of this honorific (Augusta) to his wife. Since there was no "title" of Empress(-consort) whatsoever, women of the reigning dynasty sought to be granted this honorific, as the highest attainable goal. Few were however granted the title, and certainly not as a rule all wives of reigning Emperors.

Imperator (as, for example, in Pliny the Elder's Naturalis Historia). In the Roman Republic Imperator meant "(military) commander". In the late Republic, as in the early years of the new monarchy, Imperator was a title granted to Roman generals by their troops and the Roman Senate after a great victory, roughly comparable to field marshal (head or commander of the entire army). For example, in AD 15 Germanicus was proclaimed Imperator during the reign of his adoptive father Tiberius. Soon thereafter "Imperator" became however a title reserved exclusively for the ruling monarch. This led to "Emperor" in English and, among other examples, "Empereur" in French and "Mbreti" in Albanian. The Latin feminine form Imperatrix only developed after "Imperator" had taken on the connotation of "Emperor".

Autokrator (Αὐτοκράτωρ) or Basileus (βασιλεύς): although the Greeks used equivalents of "Caesar" (Καίσαρ, Kaisar) and "Augustus" (in two forms: transliterated as Αὔγουστος, Augoustos or translated as Σεβαστός, Sebastos) these were rather used as part of the name of the Emperor than as an indication of the office. Instead of developing a new name for the new type of monarchy, they used αὐτοκράτωρ (autokratōr, only partly overlapping with the modern understanding of "autocrat") or βασιλεύς (basileus, until then the usual name for "sovereign"). Autokratōr was essentially used as a translation of the Latin Imperator in Greek-speaking part of the Roman Empire, but also here there is only partial overlap between the meaning of the original Greek and Latin concepts. For the Greeks Autokratōr was not a military title, and was closer to the Latin dictator concept ("the one with unlimited power"), before it came to mean Emperor. Basileus appears not to have been used exclusively in the meaning of "emperor" (and specifically, the Roman/Byzantine emperor) before the 7th century, although it was a standard informal designation of the Emperor in the Greek-speaking East.

The Principate (27 BC – 284 AD) period was succeeded by what is known as the Dominate (284 AD – 527 AD), during which Emperor Diocletian tried to put the Empire on a more formal footing. Diocletian sought to address the challenges of the Empire's now vast geography and the instability caused by the informality of succession by the creation of co-emperors and junior emperors. At one point, there were as many as five sharers of the imperium (see: Tetrarchy). In 325 AD Constantine I defeated his rivals and restored single emperor rule, but following his death the empire was divided among his sons. For a time the concept was of one empire ruled by multiple emperors with varying territory under their control, however following the death of Theodosius I the rule was divided between his two sons and increasingly became separate entities. The areas administered from Rome are referred to by historians the Western Roman Empire and those under the immediate authority of Constantinople called the Eastern Roman Empire or (after the Battle of Yarmouk in 636 AD) the Later Roman or Byzantine Empire. The subdivisions and co-emperor system were formally abolished by Emperor Zeno in 480 AD following the death of Julius Nepos last Western Emperor and the ascension of Odoacer as the de facto King of Italy in 476 AD.

Under Justinian I, reigning in the 6th century, parts of Italy were for a few decades (re)conquered from the Ostrogoths: thus, this famous mosaic, featuring the Byzantine emperor in the center, can be admired at Ravenna.

Historians generally refer to the continuing Roman Empire in the east as the Byzantine Empire after Byzantium, the original name of the town that Constantine I would elevate to the Imperial capital as New Rome in AD 330. (The city is more commonly called Constantinople and is today named Istanbul). Although the empire was again subdivided and a co-emperor sent to Italy at the end of the fourth century, the office became unitary again only 95 years later at the request of the Roman Senate and following the death of Julius Nepos, last Western Emperor. This change was a recognition of the reality that little remained of Imperial authority in the areas that had been the Western Empire, with even Rome and Italy itself now ruled by the essentially autonomous Odoacer.

These Later Roman "Byzantine" Emperors completed the transition from the idea of the Emperor as a semi-republican official to the Emperor as an absolute monarch. Of particular note was the translation of the Latin Imperator into the Greek Basileus, after Emperor Heraclius changed the official language of the empire from Latin to Greek in AD 620. Basileus, a title which had long been used for Alexander the Great was already in common usage as the Greek word for the Roman emperor, but its definition and sense was "King" in Greek, essentially equivalent with the Latin Rex. Byzantine period emperors also used the Greek word "autokrator", meaning "one who rules himself", or "monarch", which was traditionally used by Greek writers to translate the Latin dictator. Essentially, the Greek language did not incorporate the nuances of the Ancient Roman concepts that distinguished imperium from other forms of political power.

In general usage, the Byzantine imperial title evolved from simply "emperor" (basileus), to "emperor of the Romans" (basileus tōn Rōmaiōn) in the 9th century, to "emperor and autocrat of the Romans" (basileus kai autokratōr tōn Rōmaiōn) in the 10th.[2] In fact, none of these (and other) additional epithets and titles had ever been completely discarded.

One important distinction between the post Constantine I (reigned AD 306–337) emperors and their pagan predecessors was cesaropapism, the assertion that the Emperor (or other head of state) is also the head of the Church. Although this principle was held by all emperors after Constantine, it met with increasing resistance and ultimately rejection by bishops in the west after the effective end of Imperial power in there. This concept became a key element of the meaning of "emperor" in the Byzantine and Orthodox east, but went out of favor with in the west with the rise of Roman Catholicism.

The Byzantine empire also produced three women who effectively governed the state: the Empress Irene and the Empresses Zoe and Theodora.

In 1204 Constantinople fell to the Venetians and the Franks in the Fourth Crusade. Following the tragedy of the horrific sacking of the city, the conquerors declared a new "Empire of Romania", known to historians as the Latin Empire of Constantinople, installing Baldwin IX, Count of Flanders, as Emperor. However, Byzantine resistance to the new empire meant that it was in constant struggle to establish itself. Byzantine Emperor Michael VII Palaiologos succeeded in recapturing Constantinople in 1261. The Principality of Achaea, a vassal state the empire had created in Morea (Greece) intermittently continued to recognize the authority of the crusader emperors for another half century. Pretenders to the title continued among the European nobility until circa 1383.

With Constantinople occupied, claimants to the imperial succession styled themselves as emperor in the chief centers of resistance: The Laskarid dynasty in the Empire of Nicaea, the Komnenid dynasty in the Empire of Trebizond and the Doukid dynasty in the Despotate of Epirus. In 1248, the Epirus recognized the Nicaean Emperors, who then recaptured Constantinople in 1261. The Trebizond emperor formally submitted in Constantinople in 1281,[3] but frequently flouted convention by styling themselves emperor back in Trebizond thereafter.

Agostino Veneziano's engraving of Ottoman emperor Suleiman the Magnificent.[4] Note the four tiers on the helmet, which he had commissioned from Venice, symbolizing his imperial power, and excelling the three-tiered papal tiara.[5] This tiara was made for 115,000 ducats and offered to Suleiman by the French ambassador Antonio Rincon in 1532.[6] This was a most atypical piece of headgear for a Turkish sultan, which he probably never normally wore, but which he placed beside him when receiving visitors, especially ambassadors. It was crowned with an enormous feather.[7]

After the Ottoman capture of Constantinople in 1453, the Ottoman sultans began to style themselves Kaysar-i Rum (Emperor of the Romans) as they asserted themselves to be the heirs to the Roman empire by right of conquest. The title was of such importance to them that it led them to eliminate the various Byzantine successor states — and therefore rival claimants — over the next eight years. Though the term "emperor" was rarely used by Westerners of the Ottoman sultan, it was generally accepted by Westerners that he had imperial status.

The Roman of the Emperor's title was a reflection of the translatio imperii (transfer of rule) principle that regarded the Holy Roman Emperors as the inheritors of the title of Emperor of the Western Roman Empire, despite the continued existence of the Roman Empire in the east.

From the time of Otto the Great onward, much of the former Carolingian kingdom of Eastern Francia became the Holy Roman Empire. The prince-electors elected one of their peers as King of the Romans and King of Italy before being crowned by the Pope. The Emperor could also pursue the election of his heir (usually a son) as King, who would then succeed him after his death. This junior King then bore the title of Roman King (King of the Romans). Although technically already ruling, after the election he would be crowned as emperor by the Pope. The last emperor to be crowned by the pope was Charles V; all emperors after him were technically emperors-elect, but were universally referred to as Emperor.

The first Austrian Emperor was the last Holy Roman Emperor Francis II. In the face of aggressions by Napoleon, Francis feared for the future of the Holy Roman Empire. He wished to maintain his and his family's Imperial status in the event that the Holy Roman Empire should be dissolved, as it indeed was in 1806 when an Austrian-led army suffered a humiliating defeat at the Battle of Austerlitz. After which, the victorious Napoleon proceeded to dismantle the old Reich by severing a good portion from the empire and turning it into a separate Confederation of the Rhine. With the size of his imperial realm significantly reduced, Francis II, Holy Roman Emperor became Francis I, Emperor of Austria. The new imperial title may have sounded less prestigious than the old one, but Francis' dynasty continued to rule from Austria and a Habsburg monarch was still an emperor (Kaiser), and not just merely a king (König), in name.

The title lasted just a little over one century until 1918, but it was never clear what territory constituted the "Empire of Austria". When Francis took the title in 1804, the Habsburg lands as a whole were dubbed the Kaisertum Österreich. Kaisertum might literally be translated as "emperordom" (on analogy with "kingdom") or "emperor-ship"; the term denotes specifically "the territory ruled by an emperor", and is thus somewhat more general than Reich, which in 1804 carried connotations of universal rule. Austria proper (as opposed to the complex of Habsburg lands as a whole) had been an Archduchy since the 15th century, and most of the other territories of the Empire had their own institutions and territorial history, although there were some attempts at centralization, especially during the reign of Marie Therese and her son Joseph II and then finalized in the early 19th century. When Hungary was given self-government in 1867, the non-Hungarian portions were called the Empire of Austria and were officially known as the "Kingdoms and Lands Represented in the Imperial Council (Reichsrat)". The title of Emperor of Austria and the associated Empire were both abolished at the end of the First World War in 1918, when German Austria became a republic and the other kingdoms and lands represented in the Imperial Council established their independence or adhesion to other states.

Byzantium's close cultural and political interaction with its Balkan neighbors Bulgaria and Serbia, and with Russia (Kievan Rus', then Muscovy) led to the adoption of Byzantine imperial traditions in all of these countries.

In 913, Simeon I of Bulgaria was crowned Emperor (Tsar) by the Patriarch of Constantinople and imperial regent Nicholas Mystikos outside of the Byzantine capital. In its final simplified form, the title read "Emperor and Autocrat of all Bulgarians and Romans" (Tsar i samodarzhets na vsichki balgari i gartsi in the modern vernacular). The Roman component in the Bulgarian imperial title indicated both rulership over Greek speakers and the derivation of the imperial tradition from the Romans, however this component was never recognised by the Byzantine court.

Byzantine recognition of Simeon's imperial title was revoked by the succeeding Byzantine government. The decade 914–924 was spent in destructive warfare between Byzantium and Bulgaria over this and other matters of conflict. The Bulgarian monarch, who had further irritated his Byzantine counterpart by claiming the title "Emperor of the Romans" (basileus tōn Rōmaiōn), was eventually recognized, as "Emperor of the Bulgarians" (basileus tōn Boulgarōn) by the Byzantine Emperor Romanos I Lakapenos in 924. Byzantine recognition of the imperial dignity of the Bulgarian monarch and the patriarchal dignity of the Bulgarian patriarch was again confirmed at the conclusion of permanent peace and a Bulgarian-Byzantine dynastic marriage in 927. In the meantime, the Bulgarian imperial title may have been also confirmed by the pope. The Bulgarian imperial title "tsar" was adopted by all Bulgarian monarchs up to the fall of Bulgaria under Ottoman rule. 14th-century Bulgarian literary compositions clearly denote the Bulgarian capital (Tarnovo) as a successor of Rome and Constantinople, in effect, the "Third Rome".

After Bulgaria obtained full independence from the Ottoman Empire in 1908, its monarch, who was previously styled Knyaz, [prince], took the traditional title of Tsar [king] and was recognized internationally as such.[by whom?]

The kings of the Ancien Régime and the July Monarchy used the title Empereur de France in diplomatic correspondence and treaties with the Ottoman emperor from at least 1673 onwards. The Ottomans insisted on this elevated style while refusing to recognize the Holy Roman Emperors or the Russian tsars because of their rival claims of the Roman crown. In short, it was an indirect insult by the Ottomans to the HRE and the Russians. The French kings also used it for Morocco (1682) and Persia (1715).

Napoleon relinquished the title of Emperor of the French on 6 April and again on 11 April 1814. Napoleon's infant son, Napoleon II, was recognized by the Council of Peers, as Emperor from the moment of his father's abdication, and therefore reigned (as opposed to ruled) as Emperor for fifteen days, 22 June to 7 July 1815.

Since 3 May 1814, the Sovereign Principality of Elba was created a miniature non-hereditary Monarchy under the exiled French Emperor Napoleon I. Napoleon I was allowed, by the treaty of Fontainebleau with (27 April), to enjoy, for life, the imperial title. The islands were not restyled an empire.

On 26 February 1815, Napoleon abandoned Elba for France, reviving the French Empire for a Hundred Days; the Allies declared an end to Napoleon's sovereignty over Elba on 25 March 1815, and on 31 March 1815 Elba was ceded to the restored Grand Duchy of Tuscany by the Congress of Vienna. After his final defeat, Napoleon was treated as a general by the British authorities during his second exile to Atlantic Isle of St. Helena. His title was a matter of dispute with the governor of St Helena, who insisted on addressing him as "General Bonaparte", despite the "historical reality that he had been an emperor" and therefore retained the title.[8][9][10]

Napoleon I's nephew, Napoleon III, resurrected the title of emperor on 2 December 1852, after establishing the Second French Empire in a presidential coup, subsequently approved by a plebiscite. His reign was marked by large scale public works, the development of social policy, and the extension of France's influence throughout the world. During his reign, he also set about creating the Second Mexican Empire (headed by his choice of Maximilian I of Mexico, a member of the House of Habsburg), to regain France's hold in the Americas and to achieve greatness for the 'Latin' race.[11] Napoleon III was deposed on 4 September 1870, after France's defeat in the Franco-Prussian War. The Third Republic followed and after the death of his son Napoleon (IV), in 1879 during the Zulu War, the Bonapartist movement split, and the Third Republic was to last until 1940.

The title was not exactly hereditary but self-proclaimed by those who had, wholly or partially, united the Christian northern part of the Iberian Peninsula, often at the expense of killing rival siblings. The popes and Holy Roman emperors protested at the usage of the imperial title as a usurpation of leadership in western Christendom. After Alfonso VII's death in 1157, the title was abandoned, and the kings who used it are not commonly mentioned as having been "emperors", in Spanish or other historiography.

There was no set title for the king of England before 1066 and monarchs chose to style themselves as they pleased. Imperial titles were used inconsistently beginning with Athelstan in 930 and ended with the Norman conquest of England. Empress Matilda (1102–1167) is the only British monarch commonly referred to as "emperor" or "empress", but acquired her title through her marriage to Henry V, Holy Roman Emperor.

During the rule of Henry VIII an Act of Parliament declared that 'this realm of England is an Empire...governed by one Supreme Head and King having the dignity and royal estate of the imperial Crown of the same'. This was in the context of the divorce of Catherine of Aragon and the English Reformation, to emphasize that England had never accepted the quasi-imperial claims of the papacy. Hence England and, by extension its modern successor state, the United Kingdom of Great Britain and Northern Ireland, is according to English law an Empire ruled by a King endowed with the imperial dignity. However, this has not led to the creation of the title of Emperor in England or in the United Kingdom itself.

In 1801, George III rejected the title of Emperor when offered. The only period when British monarchs held the title of Emperor in a dynastic succession started when the title Empress of India was created for Queen Victoria. The government led by Prime MinisterBenjamin Disraeli, conferred the additional title upon her by an Act of Parliament, reputedly to assuage the monarch's irritation at being, as a mere Queen, notionally inferior to her own daughter (Princess Victoria, who was the wife of the reigning German Emperor); the Indian Imperial designation was also formally justified as the expression of Britain succeeding the former Mughal Emperor as suzerain over hundreds of princely states. The title was relinquished by George VI when India became independent on 15 August 1947.

After his death he was succeeded by his son Frederick III who was only emperor for 99 days. In the same year his son Wilhelm II became the third emperor within a year. He was the last German emperor. After the empire's defeat in World War I the empire ceased to exist.

In 1472, the niece of the last Byzantine emperor, Sophia Palaiologina, married Ivan III, grand prince of Moscow, who began championing the idea of Russia being the successor to the Byzantine Empire. This idea was represented more emphatically in the composition the monk Filofej addressed to their son Vasili III. After ending Muscovy's dependence on its Mongol overlords in 1480, Ivan III began the usage of the titles Tsar and Autocrat (samoderzhets ). His insistence on recognition as such by the emperor of the Holy Roman Empire since 1489 resulted in the granting of this recognition in 1514 by Emperor Maximilian I to Vasili III. His son Ivan IV emphatically crowned himself Tsar of Russia on 16 January 1547. The word "Tsar" derives from Latin Caesar, but this title was used in Russia as equivalent to "King"; the error occurred when medieval Russian clerics referred to the biblical Jewish kings with the same title that was used to designate Roman and Byzantine rulers — "Caesar".

On 31 October 1721, Peter I was proclaimed Emperor by the Senate. The title used was Latin "Imperator", which is a westernizing form equivalent to the traditional Slavic title "Tsar". He based his claim partially upon a letter discovered in 1717 written in 1514 from Maximilian I to Vasili III, in which the Holy Roman Emperor used the term in referring to Vasili.

A formal address to the ruling Russian monarch adopted thereafter was 'Your Imperial Majesty'. The crown prince was addressed as 'Your Imperial Highness'.

The title has not been used in Russia since the abdication of Emperor Nicholas II on 15 March 1917.

Imperial Russia produced four reigning Empresses, all in the eighteenth century.

In 1345, the Serbian King Stefan Uroš IV Dušan proclaimed himself Emperor (Tsar) and was crowned as such at Skopje on Easter 1346 by the newly created Serbian Patriarch, and by the Patriarch of Bulgaria and the autocephalous Archbishop of Ohrid. His imperial title was recognized by Bulgaria and various other neighbors and trading partners but not by the Byzantine Empire. In its final simplified form, the Serbian imperial title read "Emperor of Serbs and Greeks" (цар Срба и Грка in modern Serbian). It was only employed by Stefan Uroš IV Dušan and his son Stefan Uroš V in Serbia (until his death in 1371), after which it became extinct. A half-brother of Dušan, Simeon Uroš, and then his son Jovan Uroš, claimed the same title, until the latter's abdication in 1373, while ruling as dynasts in Thessaly. The "Greek" component in the Serbian imperial title indicates both rulership over Greeks and the derivation of the imperial tradition from the Romans.

The Aztec and Inca traditions are unrelated to one another. Both were conquered under the reign of King Charles I of Spain who was simultaneously emperor-elect of the Holy Roman Empire during the fall of the Aztecs and fully emperor during the fall of the Incas. Incidentally by being king of Spain, he was also Roman (Byzantine) emperor in pretence through Andreas Palaiologos. The translations of their titles were provided by the Spanish.

The only pre-Columbian South American rulers to be commonly called emperors were the Sapa Inca of the Inca Empire (1438–1533). Spanish conquistador Francisco Pizarro, conquered the Inca for Spain, killed Emperor Atahualpa, and installed puppets as well. Atahualpa may actually be considered a usurper as he had achieved power by killing his half-brother and he did not perform the required coronation with the imperial crown mascaipacha by the Huillaq Uma (high priest).

After the fall of Napoleon I and the Liberal revolution in Portugal, the Portuguese Royals returned to Europe (1820). Prince Pedro of Braganza (King João's older son) stayed in South America acting as regent of the local kingdom, but, two years later in 1822, he proclaimed himself Pedro I, first Emperor of Brazil. He did, however, recognize his father, João VI, as Titular Emperor of Brazil —a purely honorific title—until João VI's death in 1826.

The empire came to an end in 1889, with the overthrow of Emperor Pedro II (Pedro I's son and successor), when the Brazilian republic was proclaimed.

In Mexico, the First Mexican Empire was the first of two empires created. After the declaration of independence on September 15, 1821, it was the intention of the Mexican parliament to establish a commonwealth whereby the King of Spain, Ferdinand VII, would also be Emperor of Mexico, but in which both countries were to be governed by separate laws and with their own legislative offices. Should the king refuse the position, the law provided for a member of the House of Bourbon to accede to the Mexican throne.

Ferdinand VII, however, did not recognize the independence and said that Spain would not allow any other European prince to take the throne of Mexico. By request of Parliament, the president of the regency Agustín de Iturbide was proclaimed emperor of Mexico on 12 July 1822 as Agustín I. Agustín de Iturbide was the general who helped secure Mexican independence from Spanish rule, but was overthrown by the Plan of Casa Mata.

In Persia, from the time of Darius the Great, Persian rulers used the title "King of Kings" (Shahanshah in Persian) since they had dominion over peoples from the borders of India to the borders of Greece and Egypt. Alexander probably crowned himself shahanshah after conquering Persia[citation needed], bringing the phrase basileus toon basileoon to Greek. It is also known that Tigranes the Great, king of Armenia, was named as the king of kings when he made his empire after defeating the Parthians. Georgian title "mephet'mephe" has the same meaning.

The last shahanshah (Mohammad Reza Pahlavi) was ousted in 1979 following the Iranian Revolution. Shahanshah is usually translated as king of kings or simply king for ancient rulers of the Achaemenid, Arsacid, and Sassanid dynasties, and often shortened to shah for rulers since the Safavid dynasty in the 16th century. Iranian rulers were typically regarded in the West as emperors.

The Sanskrit word for emperor is Samrāṭ (word stem: samrāj) or Chakravarti. This word has been used as an epithet of various Vedic deities, like Varuna, and has been attested in the Rig-Veda, possibly the oldest compiled book among the Indo-Europeans. Chakravarti refers to the king of kings. A Chakravarti is not only a sovereign ruler but also has feudatories.

Typically, in the later Vedic age, a Hindu high king (Maharajah) was only called Samrāṭ after performing the Vedic Rajasuya sacrifice, enabling him by religious tradition to claim superiority over the other kings and princes. Another word for emperor is sārvabhaumā. The title of Samrāṭ has been used by many rulers of the Indian subcontinent as claimed by the Hindu mythologies. In proper history, most historians call Chandragupta Maurya the first samrāṭ (emperor) of the Indian subcontinent, because of the huge empire he ruled. The most famous emperor was his grandson Ashoka the Great. Other dynasties that are considered imperial by historians are the Kushanas, Guptas, Vijayanagara, Kakatiya, Hoysala and the Cholas.

Rudhramadevi (1259–1289) was one of the most prominent rulers of the Kakatiya dynasty on the Deccan Plateau, being one of the few ruling queens (empress) in Indian history.

After India was invaded by the Mongol Khans and Turkic Muslims, the rulers of their major states on the subcontinent were titled Sultān, In this manner, the only empress-regnant ever to have actually sat on the throne of Delhi was Razia Sultan. The Mughal Emperors were the only Indian rulers for whom the term was consistently used by Western contemporaries. For the period from 1877 to 1947 when British Emperors ruled British India as the pearl in the crown of the British Empire, see above.

In Ethiopia, the Solomonic dynasty used, beginning in 1270, the title of "nəgusä nägäst" which is literally "King of Kings". The use of the king of kings style began a millennium earlier in this region, however, with the title being used by the Kings of Aksum, beginning with Sembrouthes in the 3rd century. Another title used by this dynasty was "Itegue Zetopia".

"Itegue" translates as Empress, and was also used by the only female reigning Empress, Zauditu, along with the official title Negiste Negest (Queen of Kings).

The rulers of China and (once Westerners became aware of the role) Japan were always accepted in the West as emperors, and referred to as such. The claims of other East Asian monarchies to the title may have been accepted for diplomatic purposes, but it was not necessarily used in more general contexts.

The East Asian tradition is different from the Roman tradition, having arisen separately. What links them together is the use of the Chinese logographs 皇 (huáng) and 帝 (dì) which together or individually are imperial. Because of the cultural influence of China, China's neighbors adopted these titles or had their native titles conform in hanzi. Anyone who spoke to the emperor was to address him as bìxià (陛下, lit. the "Bottom of the Steps"), corresponding to "Imperial Majesty"; shèngshàng (聖上, lit. Holy Highness); or wànsuì (萬歲, lit. "You, of Ten Thousand Years").

In 221 BC, Ying Zheng, who was king of Qin at the time, proclaimed himself Shi Huangdi (始皇帝), which translates as "first emperor". Huangdi is composed of huang ("august one", 皇) and di ("sage-king", 帝), and referred to legendary/mythological sage-emperors living several millennia earlier, of which three were huang and five were di. Thus Zheng became Qin Shi Huang, abolishing the system where the huang/di titles were reserved to dead and/or mythological rulers. Since then, the title "king" became a lower ranked title, and later divided into two grades. Although not as popular, the title 王 wang (king or prince) was still used by many monarchs and dynasties in China up to the Taipings in the 19th century. 王 is pronounced vương in Vietnamese, ō in Japanese, and wang in Korean.

The imperial title continued in China until the Qing Dynasty was overthrown in 1912. The title was briefly revived from 12 December 1915 to 22 March 1916 by President Yuan Shikai and again in early July 1917 when General Zhang Xun attempted to restore last Qing emperor Puyi to the throne. Puyi retained the title and attributes of a foreign emperor, as a personal status, until 1924. After the Japanese occupied Manchuria in 1931, they proclaimed it to be the Empire of Manchukuo, and Puyi became emperor of Manchukuo. This empire ceased to exist when it was occupied by the Soviet Red Army in 1945.[citation needed]

In general, an emperor would have one empress (Huanghou, 皇后) at one time, although posthumous entitlement to empress for a concubine was not uncommon. The earliest known usage of huanghou was in the Han Dynasty. The emperor would generally select the empress from his concubines. In subsequent dynasties, when the distinction between wife and concubine became more accentuated, the crown prince would have chosen an empress-designate before his reign. Imperial China produced only one reigning empress, Wu Zetian, and she used the same Chinese title as an emperor (Huangdi, 皇帝). Wu Zetian then reigned for about 15 years (690–705 AD).

The earliest Emperor recorded in Kojiki and Nihon Shoki is Emperor Jimmu, who is said to be a descendant of Amaterasu's grandson Ninigi who descended from Heaven (Tenson kōrin). If one believes what is written in Nihon Shoki, the Emperors have an unbroken direct male lineage that goes back more than 2,600 years.

In ancient Japan, the earliest titles for the sovereign were either ヤマト大王/大君 (yamato ōkimi, Grand King of Yamato), 倭王/倭国王 (waō/wakokuō, King of Wa, used externally), or 治天下大王 (amenoshita shiroshimesu ōkimi, Grand King who rules all under heaven, used internally). As early as the 7th century the word 天皇 (which can be read either as sumera no mikoto, divine order, or as tennō, Heavenly Emperor, the latter being derived from a Tang Chinese term referring to the Pole star around which all other stars revolve) began to be used. The earliest use of this term is found on a wooden slat, or mokkan, unearthed in Asuka-mura, Nara Prefecture in 1998. The slat dated back to the reign of Emperor Temmu and Empress Jitō. The reading 'Tennō' has become the standard title for the Japanese sovereign up to the present age. The term 帝 (mikado, Emperor) is also found in literary sources.

Japanese monarchs were given their official title by the Chinese emperor. The new Japanese monarch after coming into power would send a representative to China and receive the anointment. They would receive their official title on several golden plates of several meters tall. Since the Japanese monarchs changed their title to 天皇 (Heavenly Emperor) in 607, the Chinese emperor refused to anoint the Japanese king, thus, ending relations with Japan for the next few hundred years.[15] Although the Japanese emperors used Chinese imperial titles,[citation needed], rarely was the Chinese-style "Son of Heaven" used. In the Japanese language, the word tennō is restricted to Japan's own monarch; kōtei (皇帝) is used for foreign emperors. Historically, retired emperors often kept power over a child-emperor as de facto regent. For a fairly long time, a shōgun (formally the imperial generalissimo, but made hereditary) or an imperial regent wielded actual political power. In fact, through much of Japanese history, the emperor has been little more than a figurehead.

After World War II, all claims of divinity were dropped (see Ningen-sengen). The Diet acquired all prerogative powers of the Crown, reverting the latter to a ceremonial role.[16] By the end of the 20th century, Japan was the only country with an emperor on the throne.

Currently, many[who?] believe the new prince of Japan will ascend the throne, as the law defines. Historically, Japan has had eight reigning empresses who used the genderless title Tennō, rather than the female consort title kōgō (皇后) or chūgū (中宮). There is ongoing discussion of the Japanese Imperial succession controversy. Although current Japanese law prohibits female succession, all Japanese emperors claim to trace their lineage to Amaterasu, the Sun Goddess of the Shintōreligion. Thus, the Emperor is thought to be the highest authority of the Shinto religion, and one of his duties is to perform Shinto rituals for the people of Japan.

The rulers of Goguryeo (37 BC-668 AD) used the title of Taewang (Hangul: 태왕, Hanja:太王), literally translated as the Greatest of the Kings. Also some Silla (57 BC-935 AD) rulers including Beopheung and Jinheung used this title for their declaration of independence from the influence of Goguryeo.

The rulers of Balhae (698–926) internally called themselves Seongwang (Hangul: 성왕, Hanja: 聖王).[18] In the 10th century, Gwangjong of Goryeo took the title of emperor himself as a means of enhancing the prestige of the monarchy, and it was first used in Korea. Many Goryeo sovereign alternately used both supreme king and emperor. After the Mongolian invasions (1231–1258), however, Korea relinquished the imperial title.

In 1897, King Gojong proclaimed the founding of the Korean Empire (1897–1910), and became emperor of Korea. Emperor Gojong declared the new era name "Gwangmu" (Hangul: 광무, Hanja: 光武, Warrior of light). The Korean Empire maintained their state until 1910 — though it was an Empire by name, it was in fact in the process of being absorbed by Japan.

Pre-Mongol Kingdoms such as the Xiongnu used the title "Chanu" meaning "Ruler of all" in old Mongolian. However it was not until the Chanu name was dropped and instead replaced by "Khan" that the rulers of Mongolia claimed the divine right as the ruler of all under the blue sky, this rule was closely tied with the ancient religious beliefs of the people of Mongolia (Tengrism). The title Khagan (khan of khans or grand khan) was held by Genghis Khan, founder of the Mongol Empire in 1206. After 1271, the emperors of the Yuan Dynasty also took the Chinese title huangdi, or Chinese emperor. Only the Khagans from Genghis Khan to the fall of the Yuan Dynasty in 1368 are normally referred to as Emperors in English.

Ngô Quyền, the first ruler of Đại Việt as an independent state, used the title Vương (王, King). However, after the death of Ngô Quyền, the country immersed in a civil war known as Chaos of the 12 Lords that lasted for over 20 years. In the end, Đinh Bộ Lĩnh unified the country after defeating all the warlords and became the first ruler of Đại Việt to use the title Hoàng Đế (皇帝, Emperor) in 968. Succeeding rulers in Vietnam then continued to use this Emperor title until 1806 when this title was stopped being used for a century.

Đinh Bộ Lĩnh wasn't the first to claim the title of Đế (帝, Emperor). Before him, Lý Bí and Mai Thúc Loan also claimed this title. However, their rules were very short lived.

The Vietnamese emperors also gave this title to their ancestors who were lords or influence figures in the previous dynasty like the Chinese emperors. This practice is one of many indications of the idea "Vietnam's equality with China" which remained intact up to the twentieth century.[19]

In 1802 the newly established Nguyễn dynasty requested canonization from Chinese Jiaqing Emperor and received the title Quốc Vương (國王, King of a State) and the name of the country as An Nam (安南) instead Đại Việt (大越). To avoid unnecessary armed conflicts, the Vietnamese rulers accepted this in diplomatic relation and use the title Emperor only domestically. However, Vietnamese rulers never accepted the vassalage relationship with China and always refused to come to Chinese courts to pay homage to Chinese rulers (a sign of vassalage acceptance). China waged a number of wars against Vietnam throughout history, and after each failure, settled for the tributary relationship. The Yuan dynasty under Kublai Khan waged three wars against Vietnam to force it into a vassalage relationship but after successive failures, Kublai Khan's successor, Temür Khan, finally settled for a tributary relationship with Vietnam. Vietnam sent tributary missions to China once in three years (with some periods of disruptions) until the 19th century, Sino-French War France replaced China in control of northern Vietnam.

The emperors of the last dynasty of Vietnam continued to hold this title until the French conquered Vietnam. The emperor, however, was then a puppet figure only and could easily be disposed of by the French for more pro-France figure. Japan took Vietnam from France and the Axis-occupied Vietnam was declared an empire by the Japanese in March 1945. The line of emperors came to an end with Bảo Đại, who was deposed after the war, although he later served as head of state of South Vietnam from 1949-55.

^Notice that, before the emergence of the modern country of Spain (beginning with the union of Castile and Aragon in 1492), the Latin word Hispania, in any of the Iberian Romance languages, either in singular or plural forms (in English: Spain or Spains), was used to refer to the whole of the Iberian Peninsula, and not exclusively, as in modern usage, to the country of Spain, thus excluding Portugal.

^Although the Emperor of Japan is classified as constitutional monarch among political scientists, the current constitution of Japan defines him only as 'a symbol of the nation' and no subsequent legislation states his status as the (head of state) or equates the Crown synonymously with any government establishment.